The present invention relates to locking devices, and particularly to key-operated door locking devices for preventing forced entry by unauthorized persons into enclosed spaces, such as buildings, rooms, cabinets, safes, and the like.
The invention is particularly useful with the conventional rim locks of the type which includes a cylinder within the lock casing and rotatable upon the insertion of the proper key into the keyhole, and a dog carried by the cylinder engageable with a bolt for projecting and withdrawing the bolt into and out of a recess in the door frame. One of the drawbacks of such conventional rim locks, is that they are usually not particularly difficult to open by the insertion of an instrument between the locking bolt and the door frame to force the bolt back into the lock casing.
A number of door locking devices have been devised which include rods projectable from a plurality of sides of the door into recesses formed in the door frame. One such locking device includes a handle which is released for rotation by the insertion of the proper key, the handle causing the rods to be projected and withdrawn. Such a locking device, however, is of costly construction and is used primarily in expensive safes and the like.
Another such locking device includes an arrangement wherein the rods are pivotably mounted to a rotatable member located in the center of the door; the rotatable member is rotated by teeth formed on the lock cylinder which cylinder is rotated by the insertion of the proper key in the keyhole.
Such a device, however, requires two keys to be used, one for the normal rim lock mounted adjacent to one side of the door, and the other for the special centrally-mounted locking device which actuates the rods.